Friday 8-28 (B) and Monday 8-31 (A) Accuracy and Precision Mrs. Wilson

Major Quiz 1-3 Collect a periodic table. This can be used to cover up your quiz. Calculators are not necessary. Work by yourself. Work silently. Do NOT do question #21’s “Closest fire alarm station” or “Waste disposal container” Follow the LASA honor code. There is a back! Turn in your completed quiz into the Class In Bin, and return the periodic table.

Agenda 1. Major Quiz Accuracy and Precision 3. Intensive vs. Extensive Properties 4. Types of Error 5. Percent Error Calculation 6. Accuracy and Precision Mini-Lab 7. Exit Ticket

Objectives 1. Describe and understand the importance of having accurate and precise measurements. 2. Describe, understand and differentiate between intensive and extensive properties. 3. Describe how to minimize both determinate and indeterminate error. 4. Calculate percent error and determine why percent error may be too high. HOMEWORK 1.3 Homework and Lab Questions – Daily Quiz 1-4 Next Class

The Hand Signal If I need your quiet attention, I’ll raise my hand and stop speaking. If you raise your hand and go quiet, we can get started quicker!

Engage Discuss with a partner or your table: What makes being “accurate” different from being “precise”? Are both traits important? How?

1.3 Accuracy vs. Precision (pg 6) Accuracy: the degree of closeness of measurements of a quantity to that quantity's actual (true) value. Precision: also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results. Discuss with a partner: Describe any real-life situation where both accuracy and precision are vital to success.

1.3: Uncertainty and reliability Uncertainty: An estimate attached to a measurement which defines the range of values within which the true value lies. You can decrease your uncertainty by making accurate and precise measurements. Ex ± 0.1 mL Reliability: A measurement with a minimized uncertainty. Uncertainty ≠ Reliability The uncertainty of this measurement

1.3 Intensive vs. Extensive Properties Intensive - Properties that do not depend on the amount of the matter present. Color / Odor / Luster - How shiny a substance is. (“Lustrous” or “not lustrous”) Turbidity – How cloudy a liquid is. (“Clear”, “transparent”, “opaque”) Specific Heat – How many J of energy that 1 g of a solid absorbs to raise its temperature by 1 °C Malleability - The ability of a substance to be beaten into thin sheets. Ductility - The ability of a substance to be drawn into thin wires. Conductivity - The ability of a substance to allow the flow of energy or electricity. Hardness - How easily a substance can be scratched. Melting/Freezing Point - The temperature at which the solid and liquid phases of a substance are in equilibrium at atmospheric pressure. Boiling Point - The temperature at which the vapor pressure of a liquid is equal to the pressure on the liquid (generally atmospheric pressure). Density - The mass of a substance divided by its volume

Intensive vs. Extensive Properties Extensive - Properties that do depend on the amount of matter present. Mass - A measurement of amount of matter in a object (g) Weight - A measurement of the gravitational force of attraction of the earth acting on an object. Volume - A measurement of the amount of space a substance occupies. Length or Distance or Height or Width # of Particles (or # of Moles)

Intensive and Extensive Properties List some intensive and extensive properties of the water in each piece of glassware. Which glassware reduces uncertainty the best? How do you know? To read volume in glassware with increased precision, record one additional digit after the “certain” ones. Ex. Volume = mL

Practice Questions on Intensive vs. Extensive Mix/Pair/Share Find a partner from another table, sit with them, and work on practice questions #1-3 in the packet.

Practice Questions on Intensive vs. Extensive 1. Which of the following is an intensive property of a box of raisins? a. Calories per serving b. Total grams c. Total number of raisins d. Total calories

Practice Questions on Intensive vs. Extensive 2. Which of the following is an extensive property of a sample of gold? a. Density of 19.3 g/cm 3 b. Melts at 1063 °C c. Weighs 30.0 g d. Yellow

Practice Questions on Intensive vs. Extensive 3. Which of the following are extensive properties of coffee in a mug? a. total mg of caffeine b. cream added per mL of coffee c. temperature d. percent sugar

Practice Questions on Intensive vs. Extensive Describe some intensive properties of the solid on the weighing paper. Describe some extensive properties of the solid on the weighing paper. Be as accurate as possible!

Types of Error Determinate Error: have a definite direction and magnitude and have an assignable cause (their cause can be determined). Determinate error is also called systematic error. Determinate error can (theoretically) be eliminated. Indeterminate Error: = random error, or noise. Indeterminate error can be minimized but cannot be eliminated. Percent Error: expresses as a percentage the difference between an approximate or measured value and an exact or known value.

Mix/Pair/Share Determinate or indeterminate? Recording a mass of g as g. The mass reading on an electronic balance fluctuates between and g. A calibrated 100. g weight causes a mass reading of 101. g. The lines on a graduated cylinder have rubbed off. Spilling some chemical on the tabletop when you are transferring it between a beaker and a test tube

Do you get it? The accepted value for density of an object is 5.00 ± 0.10 g/cm 3. Is each set accurate, precise, not accurate, not precise? Are the values reliable? Are they uncertain? If there is error, what type of error(s) are occurring situation and what could have happened to cause the error(s)? 4.09 g/cm 3, 5.22 g/cm 3, 4.82 g/cm g/cm 3, 5.44 g/cm 3, 5.47 g/cm g/cm 3, 5.03 g/cm 3, 4.88 g/cm 3

% Error Calculation Example If a student measures the length of the desk to be 1.23 m and the actual length of the desk is 1.25 m, what is the student’s PE?

Accuracy and Precision Mini Lab at Desk (pg. 7) Lab Objective: The student will be able to distinguish between the accuracy and precision of estimates made of the measure of several different quantities. Form your own groups of 2 – 3. Supply your own paper. Rulers are available up at the front. Wait for the signal – then perform the lab, collect data and answer the questions with your partner.

1. Which of your two sets of estimates was most accurate (1-4 or 5-8)? Explain why you think this occurred and justify your answer. (Use data from your table.) 2. Which of the two sets of estimates was most precise? Again, justify your answer? 3. Is the most accurate set also the most precise? Do they have to be? Explain. 4. Would the following be determinate (D) or indeterminate (I) error in the above activity? Your ruler is missing calibration marks on the portion used to measure the length. You always make your measurement starting at 1 cm instead of 0 cm. Your ruler has inaccurate calibration marks made by the manufacturer.

Exit Ticket End of Class Procedure: Complete and turn in your exit ticket by yourself. You may not use any notes. Put your books etc. away. Wait for dismissal. Clean up your table. When you are dismissed by me (not the bell), push in your chairs straight as you leave. Homework: Pg. 7-8 (lab questions) and 1.3 Homework. You will have Daily Quiz 1-4 at the beginning of next class.